This invention relates to an endoscopic apparatus primarily intended for medical use. More particularly, the invention relates to an endoscopic apparatus using an extremely fine composite optical fiber as an integral assembly of an image transmitting optical fiber for use in the finding and diagnosis of a lesion and a large-diameter, laser transmitting optical fiber for use in the treatment of the lesion.
Heretofore, endoscopes using a fused monolithic image fiber or an optical fiber such as an image bundle have been commercialized in various types. Transmitting laser light to the lesion over the optical fiber is also a commercialized technique in laser therapy.
Conventionally, the endoscope and the laser transmitting optical fiber are physically independent of each other and must be inserted into the human body either through separate holes or via the lumens of catheter tubes.
In a non-medical field and for the purpose of cutting and welding metals, laser machining methods and systems have been proposed and they employ a composite optical fiber that consists of a large-diameter, machining laser light transmitting fiber surrounded by a large number of image transmitting fibers that are bundled together to form an integral assembly with the central fiber (see, for example, JP 9-216086A, JP 9-216087A and JP 2003-1465A).
The laser machining method or system proposed by JP 2003-1465A is shown in FIG. 5; a YAG laser oscillator emits a machining laser beam which passes through an optical fiber to be guided to a laser combining dichroic beam splitter, from which the combined laser beam is reflected to get into incident optics, where it is processed to become passable through a composite optical fiber; thereafter, the laser beam travels through the composite optical fiber to be introduced into an output section, where it is focused to irradiate the work.
Illuminating laser light, on the other hand, passes through an illuminating light guiding optical fiber to be guided into the dichroic beam splitter, where it is added to the center of the machining laser; the combined laser beam enters the incident optics, where it is processed to become passable through the composite optical fiber; thereafter, the illuminating laser beam travels through the composite optical fiber to be introduced into the output section, where it is focused with the machining laser beam to irradiate the work.
The image carrying laser beam is reflected from the work and travels in opposite direction to pass through the output section, the composite optical fiber, incident optics, beam splitter and finally through an interference filter to reach a monitor unit which displays the image of the illuminated lesion.
In all conventional laser therapeutic systems, the endoscope which is responsible for image observation is physically independent of the laser light transmitting optical fiber, so the image of the lesion needs to be checked either through the endoscope or by external x-ray monitoring. With the laser light transmitting optical fiber inserted into the human body until it comes close enough to the lesion, the doctor performs treatment by applying laser light to the lesion while checking the position of the optical fiber with the aid of the image obtained from the endoscope or by x-ray monitoring.
This technique requires that the surgeon perform laser application by first making visual check of the lesion and the optical fiber either through the endoscope or by x-ray monitoring and then, on the basis of the obtained image information, exercising his or her discretion in directing the tip of the optical fiber to the desired position with respect to the lesion.
However, directing the tip of the laser illuminating optical fiber to the desired position with respect to the lesion largely depends on the skill and discretion of the operator and so does the accuracy with which the applied laser light can fall on the target position of the lesion. What is more, unwanted exposure to x-rays from the outside can cause not only a safety problem but also inconsistency in the efficacy of laser therapy.
The conventional composite optical fibers described in JP 9-216086A, JP 9-216087A and JP 2003-1465A which have a laser light transmitting section and an image transmitting section are all intended to be used under exposure to radiation or to transmit laser light of high output power. Since those composite optical fibers are fabricated from a stepped-index fiber whose core is made of pure quartz glass, it has been difficult to reduce the fiber diameter small enough to be suitable for use on endoscopes.